The proposed studies involve continued investigations of the quaternary structures of large biological molecules, particularly enzymes and nucleic acids. Major emphasis will be directed to further elucidation of the quaternary structures of biotin-containing enzymes. Transcarboxylase, a very large enzyme, consists of a core structure surrounded by as many as six outside subunits attached to the core by biotin-containing polypeptides. Better definition of the structure will be sought by EM studies involving microcrystals. Electron microscopy will be used as supplementary methods for determining the portion of the amino acid sequence of the biotinyl subunit which is essential for combination of the outer subunits to the central subunit. The structure of very low density lipoprotein (VLDL) and VLDL remnants will be investigated by electron microscopy as will be DNA-protein complexes of Adenovirus Type 5.